Walki has developed a new biomass cover with an extended width of six metres. The new, wider cover increases the amount of energy that can be derived from logging residues through significantly improved dry matter content.

“Given the growing concern for the environment, it comes as no surprise that the market for biomass is experiencing a positive trend," says Jens Desthon, Sales Manager Sweden and Norway. Desthon explains that, while logging residue is an inexpensive and accessible source of biofuel, the products have to be dried in order to deliver high energy content.

“Dry Matter Content (DMC) is the key to improving the amount of energy that can be derived from logging residues. If they’re left out in the open, they absorb moisture and the energy content declines significantly," he says.

For this reason, logging residues are first left on the ground to dry and then stored in piles for several months. To protect the piles from moisture, Walki has developed a paper-based, waterproof cover that can be incinerated with the residue. The cover shelters the top of the pile, but leaves the sides open, allowing moisture to evaporate.

However, more recently, studies have shown that simply covering the piles may not be sufficient, and that the effectiveness of a cover is linked to its size. As a result, Walki has developed a new, wider biomass cover with a width of six metres, compared with other covers that are typically four metres wide. Moreover, Walki is the only company that produces its biomass covers in Europe.

In a recent study by Skogforsk (the Forestry Research Institute of Sweden), the DMC in different piles of logging residues was compared. Some piles were covered with paper tarpaulins of varying widths – 3.1, 4 and 6 m – while others were uncovered. Compared with the uncovered piles, the 6m cover delivered a nine per cent increase in DMC, while the 3.1m and 4m tarpaulins delivered two and four per cent respectively.

One customer that has invested in Walki’s wider biomass cover is SCA Energy, a leading Swedish developer and producer of renewable energy from forest resources.

Simon Hellgren, Production Manager Biofuels, SCA Energy, says Walki’s new product allows the material to be stacked higher and wider, while providing effective protection from rain and snow.

“In our production of forest biofuels, less moisture content means more energy per transported tonne of material, lower transportation costs and fewer CO2-emissions," says Hellgren. “The 6m-biomass cover allows us to stack and cover more material per m2, resulting in less waste, reduced moisture through increased exposure to the wind and sun, and less space needed for storage – making it more cost- and energy-efficient than the 4m cover."